The present application is directed to a chemical toner containing a curable amorphous resin and sublimation colorant for a second transfer process. As described herein, the phrase “chemical toner” refers to toner prepared by newer chemical methods as contrasted with an older generation toner which is prepared by mechanical grinding processes. “Chemical toner” can be prepared by a variety of processes including for example emulsion aggregation (to result in “emulsion aggregation toner”) and suspension polymerization.
Emulsion aggregation (EA) toners are used in forming print and/or xerographic images. Emulsion aggregation techniques typically involve the formation of an emulsion of the resin particles, which particles have a small size of from, for example, about 5 to about 500 nanometers in diameter, by heating the resin, optionally with solvent if needed, in water, or by making a latex in water using an emulsion polymerization. A colorant dispersion, for example of a pigment dispersed in water, optionally also with additional resin, is separately formed. The colorant dispersion is added to the emulsion latex mixture, and an aggregating agent or complexing agent is then added and/or aggregation otherwise initiated to form aggregated toner particles. The aggregated toner particles are heated to enable coalescence/fusing, thereby achieving aggregated, fused toner particles. United States patents describing emulsion aggregation toners include, for example, U.S. Pat. Nos. 5,370,963, 5,418,108, 5,290,654, 5,278,020, 5,308,734, 5,344,738, 5,403,693, 5,364,729, 5,346,797, 5,348,832, 5,405,728, 5,366,841, 5,496,676, 5,527,658, 5,585,215, 5,650,255, 5,650,256, 5,501,935, 5,723,253, 5,744,520, 5,763,133, 5,766,818, 5,747,215, 5,827,633, 5,853,944, 5,804,349, 5,840,462, and 5,869,215.
However, chemical toners have not been employed in transfer printing processes. Transfer printing is a process in which an image is first printed onto a transfer carrier sheet and then “transferring” that image onto a permanent image-receiving surface. The transfer may be accomplished by placing the transfer carrier sheet with the image printed thereon in contact with said surface of the article, and applying either heat or force to the transfer carrier sheet until the image transfers onto the article surface.
The use of sublimable dyes in transfer printing processes has been commercially practiced for more than 50 years. Creating the images to be transferred has been accomplished using established imaging technologies such as off-set press, silk screen, and ink jet methods, or the like. The image is usually formed on paper using inks containing sublimable dye colorants. The transfer paper decals are then brought into contact with the textile or other material to be decorated and with the application of heat, about 100° C. to 300° C., and pressure, to assure intimate contact between the donor and receptor, the dye is vaporized and transferred as a gas, imagewise, to the receptor. Thus, a permanent image is fowled.
Sublimable dyes colorants are generally obtained by dispersing the subliminable dye into an aqueous solution including water, an organic solvent and a dispersant. In typical ink jet recording systems, the ink should be ejected from thin nozzles as ink droplets to ensure the ink does not smear and is printed in the desired location on the substrate. Furthermore, unlike water-soluble dyes, the sublimation colorant in the transfer printing ink tends to aggregate on the surface of the printhead nozzle and clog the printhead nozzle. This aggregation is believed to be caused by evaporation of moisture during the storage of the sublimation colorant. Still further, the water soluble organic solvent used to disperse the subliminable dye is evaporated with water during the heat treatment and can cause substantial environmental pollution and/or safety concerns.
To formulate process color thermal transfer dye sublimation toner, one must ensure that only the sublimation colorant component transfers to the secondary substrate, and thus that the remaining toner formulation remains on the transfer sheet.
For the past three decades, toners have been formulated to retard their inherent tendency to adhere to hot surfaces. For examples, as described by U.S. Pat. No. Re 31,072 to Jadwin, high molecular weight and especially cross linked polymers may be incorporated into the toner formulation. Another means of solving this problem involves the incorporation of internal lubricating agents, such as waxes. A third solution is the incorporation of inert, preferably organic fillers, such as metal oxides, carbonates and the like, to act as flatting agents and which retard tack in most resins. The incorporation of two or more of these approaches is especially effective in preventing mass transfer of the toner to the receptor substrate during sublimation transfer of the dye image.
Attempts at the inclusion of sublimable dyes into toners are seen for example, in U.S. Pat. Nos. 5,555,813 and 4,536,462, each of which are incorporated by reference herein in their entirety. U.S. Pat. No. 5,555,813 describes a toner containing a sublimable dye intended for use in the preparation of images to be transferred to a secondary substrate. U.S. Pat. No. 5,555,813 teaches, however, that in order to transfer the sublimable dye component a molecular sieve, such as a zeolite, must be included in the toner composition to assist in dye transfer. The molecular sieve retains the dye in its voids and then transfers the dye upon heating at elevated temperatures. U.S. Pat. No. 4,536,462 also discusses the use of sublimation dyes to prepare toner compositions. The toner is a monochrome, magnetic toner product. This teaching requires the inclusion of a surfactant in the composition in order to achieve good image development. As these patents demonstrate, the inclusion of sublimation dyes into toners for color processing requires special considerations.
U.S. Pat. No. 6,270,933, which is incorporated by reference herein in its entirety, describes the inclusion of a high molecular weight polyester resins with a molecular weight above about 75,000, such as about 300,000. These polymer materials do not melt and become tacky at the temperatures needed to cause sublimation of the disperse dye components, and therefore are not likely to transfer freely to the secondary substrate. However, U.S. Pat. No. 6,270,933 further describes that the use of lower molecular polyester resins, such as crystalline polyester resins and amorphous polyester resins, become very tacky and sticky at the elevated temperatures required to the sublime the sublimation dyes and thus makes clean transfer of the dye to the substrate “impossible.”